Make IOSink implement StringSink

pkg/http/lib/src/utils.dart

Index: pkg/http/lib/src/utils.dart
diff --git a/pkg/http/lib/src/utils.dart b/pkg/http/lib/src/utils.dart
index 65c47997b1e6991c5cf460fe4ae8659432901262..b626b1aa203c2cf381c0e36b8e06b5a345a86bf9 100644
--- a/pkg/http/lib/src/utils.dart
+++ b/pkg/http/lib/src/utils.dart
@@ -78,30 +78,20 @@ List<String> split1(String toSplit, String pattern) {
 Encoding encodingForCharset(
     String charset, [Encoding fallback = Encoding.ISO_8859_1]) {
   if (charset == null) return fallback;
-  var encoding = _encodingForCharset(charset);
+  var encoding = Encoding.fromName(charset);
   return encoding == null ? fallback : encoding;
 }
 
+
 /// Returns the [Encoding] that corresponds to [charset]. Throws a
 /// [FormatException] if no [Encoding] was found that corresponds to [charset].
 /// [charset] may not be null.
 Encoding requiredEncodingForCharset(String charset) {
-  var encoding = _encodingForCharset(charset);
+  var encoding = Encoding.fromName(charset);
   if (encoding != null) return encoding;
   throw new FormatException('Unsupported encoding "$charset".');
 }
 
-/// Returns the [Encoding] that corresponds to [charset]. Returns null if no
-/// [Encoding] was found that corresponds to [charset]. [charset] may not be
-/// null.
-Encoding _encodingForCharset(String charset) {
-  charset = charset.toLowerCase();
-  if (charset == 'ascii' || charset == 'us-ascii') return Encoding.ASCII;
-  if (charset == 'utf-8') return Encoding.UTF_8;
-  if (charset == 'iso-8859-1') return Encoding.ISO_8859_1;
-  return null;
-}
-
 /// Converts [bytes] into a [String] according to [encoding].
 String decodeString(List<int> bytes, Encoding encoding) {
   // TODO(nweiz): implement this once issue 6284 is fixed.